Exhaust Manifold

ABSTRACT

In an exhaust manifold, a plurality of branch pipes is bent downward from a head flange to form like an L-letter shape, where exhaust-gas upstream side end portions of the pipes are connected with an engine through the head flange and exhaust-gas downstream side end portions thereof are connected with a pipe collecting part which is provided with a sensor for detecting a state of exhaust gas. The pipe collecting part has a reduced diameter portion where a length of the pipe collecting part in a longitudinal direction of the head flange is set shorter than that of the pipe collecting part in a thickness direction of the head flange. The sensor is provided on the reduced diameter portion.

TECHNICAL FIELD

The present invention relates to an exhaust manifold which is connectedto an engine, especially an exhaust manifold provided with a sensor on apipe collecting part thereof to detect a state of an exhaust gas passingtherethrough.

BACKGROUND OF THE INVENTION

Conventional exhaust manifolds with a sensor are disclosed in JapanesePatent Applications Laid-open Publication No. 2003-83061 and No.10-26037. As shown in FIG. 8, the conventional exhaust manifolds have aplurality of branch pipes 02 with upstream side portions being bentdownward from a head flange 01 to form like an L-letter shape. Theirupstream side end portions are connected with an engine E through thehead flange 01. The downstream side end portions of the former areconnected with a catalytic converter via a pipe collecting part 06,while those of the latter are aggregated and directly connected with acatalytic converter. The former is superior to the latter, in weighsaving and high-accurate detection of a state of an exhaust gas.

The pipe collecting part 06 has a reduced diameter portion 06 d at itsintermediate position, where the reduced diameter portion 06 d has acircular cross section whose diameter is reduced compared to those ofupstream and downstream side end portions thereof. The reduced diameterportion 06 d is provided with a sensor 010 for detecting oxygenconcentration in the exhaust gas so that a sensing part 010 c of thesensor 010 is positioned in the center of a flow of the exhaust gaspassing through the reduced diameter portion 06 d to obtain highaccurate sensing.

DISCLOSURE OF THE INVENTION Problem(s) to be Solved by the Invention

The former conventional exhaust manifold, however, has the followingproblem.

In the conventional exhaust manifold, all of branch pipes 02 are bentdownward from the head flange 01 to form like an L-letter shape,exhaust-gas upstream side end portions of the branch pipes 02 are fixedto the engine E through the head flange 01, and exhaust-gas downstreamside end portions thereof are fixed to a vehicle body through acatalytic converter 07 and others. A stress is produced due to thevibrations of the engine E (A direction of the vibration is indicated byan arrow ER around a vertical axis, vertical to a paper surface of thisspecification, passing through a point OA in FIG. 8.) and also due tothermal expansion and contraction of the respective branch pipes 02 (Adirection of thermal expansion and contraction are indicated by an arrowBD in FIG. 8.), and consequently the stress acts on the exhaust manifoldso that the whole exhaust manifold may be folded like an L-letter shape.In this case, the pipe collecting part 06 and/or its periphery may verylikely buckle up at the reduced diameter portion 06 d, which isindicated by an alternate long and short dash lined ellipse AB and isweak in strength. In order to avoid this buckling, the pipe collectingpart 06 is required to increase in thickness to enforce the strength ofthe reduced diameter portion 06 d of the pipe collecting part 6. Thiscauses the problem in that a temperature rise in an exhaust gaspurifying catalyst is delayed due to the increase in weight and thermalcapacity of the pipe collecting part 06.

The present invention is made to solve the above-described problem, andan object thereof is to provide an exhaust manifold which can enforcestrength of a pipe collecting part without increasing its weight anddetect a state of an exhaust gas with high accuracy by a sensor, therebyaccelerating a temperature rise of an exhaust gas purifying catalyst toimprove an exhaust gas purifying performance.

Means for Solving the Problems

According to an aspect of the present invention, there is provided anexhaust manifold including a head flange, a plurality of branch pipes,and a pipe collecting part. The head flange is fixed to an engine. Theplurality of branch pipes is bent downward from the head flange to formlike an L-letter shape, where the branch pipes have exhaust-gas upstreamside end portions and exhaust-gas downstream side end portions. Theexhaust-gas upstream side end portions are connected with the enginethrough the head flange, and the exhaust-gas downstream side endportions of the branch pipes are connected with the pipe collectingpart. The pipe collecting part is provided with a sensor for detecting astate of an exhaust gas. The pipe collecting part has a reduced diameterportion in which a length, of the pipe collecting part, in alongitudinal direction of the head flange is set to be shorter than alength, of the pipe collecting part, in a thickness direction of thehead flange. The reduced diameter portion is provided with the sensor.

Preferably, the pipe collecting part has an intermediate portion inwhich the both surfaces seen from the thickness direction are formed tohave an involute curve.

Preferably, the pipe collecting part is formed to have curves at bothsides, respectively, so that width lengths of the surfaces seen from thethickness direction become larger from an exhaust-gas upstream side endportion of the pipe collecting part to an exhaust-gas downstream sideend portion thereof.

Preferably, the pipe collecting part has two divided bodies, which areseparatable in the longitudinal direction along the thickness direction,coupled with each other.

Preferably, the sensor has a holding portion which is fixed on one ofthe surfaces seen from the longitudinal direction through a boss memberprovided thereon.

EFFECT OF THE INVENTION

In the exhaust manifold of the present invention, the plurality ofbranch pipes is bent downward from the head flange to form the L-lettershape. The exhaust-gas upstream side end portions are connected with theengine through the head flange, and the exhaust-gas downstream side endportions of the branch. pipes are connected with the pipe collectingpart. The pipe collecting part is provided with the sensor for detectingthe state of the exhaust gas. The pipe collecting part has a reduceddiameter portion in which the length of the pipe collecting part in thelongitudinal direction of the head flange is shorter than the length ofthe pipe collecting part in the thickness direction of the head flange,and the reduced diameter being provided with the sensor.

Therefore, the exhaust manifold of the invention can increase itsstrength without increasing the weight of the pipe collecting part. Thiscan improve its exhaust gas purifying performance by promoting the risein temperature of an exhaust gas purifying catalyst. In addition, it candetect the state of the exhaust gas with high accuracy.

In the invention, the pipe collecting part has the intermediate portionin which the both surfaces seen from the thickness direction are formedto have the involute curve. Therefore, it facilitates dispersion of thestress acting on the surfaces, thereby increasing the strength of thereduced diameter portion.

In the invention, the pipe collecting part is formed to have the curvesat both sides, respectively, so that width lengths of the surfaces seenfrom the thickness direction become larger from the exhaust-gas upstreamside end portion of the pipe collecting part to the exhaust-gasdownstream side end portion thereof. Therefore, this can ensure the pipecollecting part 6 to bear the stress acting on the surfaces.

In the invention, the pipe collecting part has the two divided bodies,which are separatable in the longitudinal direction along the thicknessdirection, coupled with each other. Therefore, the pipe collecting part6 can be manufactured easily and low costs.

In the invention, the sensor has the holding portion which is fixed onthe one of the surfaces seen from the longitudinal direction through theboss member provided thereon. Therefore, strength of the surfaceprovided with the holding portion and the boss member can be increased,a projecting amount of the oxygen sensor from the pipe collecting partbeing reduced, and the oxygen sensor being avoided from possibleinterference with other portions/parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention willbecome apparent as the description proceeds when taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a front view showing an exhaust manifold of an embodimentaccording to the present invention;

FIG. 2 is a right side view showing the exhaust manifold of theembodiment;

FIG. 3 is a front view showing a pipe collecting part of the exhaustmanifold of the embodiment;

FIG. 4 is a rear view showing the pipe collecting part of the exhaustmanifold of the embodiment;

FIG. 5 is a right side view showing the pipe collecting part of theexhaust manifold of the embodiment;

FIG. 6 is a left side view showing the pipe collecting part of theexhaust manifold of the embodiment;

FIG. 7 is a plan view showing the pipe collecting part of the exhaustmanifold of the embodiment; and

FIG. 8 is a right side view showing a conventional exhaust manifold andis used for explaining its problem.

DESCRIPTION OF REFERENCE NUMBERS

-   EM exhaust manifold-   1 head flange-   1 a insertion hole-   2, 3, 4, 5 branch pipe-   6 pipe collecting part-   6 a, 6 b divided body-   6 c exhaust-gas upstream side end portion-   6 d reduced diameter portion-   6 e opening portion-   6 f exhaust-gas downstream side end portion-   7 catalytic converter-   8 catalyst carrier-   9 flange portion-   10 oxygen sensor-   10 a wiring-   10 b holding portion-   10 c sensing part-   11 boss member

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings.

Embodiment

The embodiment of the present invention will be described.

FIG. 1 is a front view showing an exhaust manifold of the embodimentaccording to the present invention, FIG. 2 is a right side view showingthe exhaust manifold, FIG. 3 is a front view showing a pipe collectingpart of the exhaust manifold, FIG. 4 is a rear view showing the same,FIG. 5 is a right side view showing the same, FIG. 6 is a left side viewshowing the same, and FIG. 7 is a plan view showing the same.

First the entire construction of the exhaust manifold EM of theembodiment will be described.

As shown in FIG. 1 and FIG. 2, the exhaust manifold EM includes a headflange 1, four branch pipes 2 to 5 and a pipe collecting part 6, and itis equipped with a catalytic converter 7 and an oxygen sensor 10.

The head flange 1 is formed like a plate and is fixed on one of sidesurfaces of a not-shown cylinder head of a not-shown engine.

The branch pipes 2 to 5 are projected in a lateral direction of theengine from the head flange 1 so that they are bent downward therefromto form like an L-letter shape.

As shown in FIG. 2, exhaust-gas upstream side end portions of the branchpipes 2 to 5 are connected to respective insertion holes 1 a formed onthe head flange 1, where the insertion holes 1 a are communicated tocylinders of the engine, respectively. Exhaust-gas downstream side endportions thereof are formed to each have a quadrant cross section to beassembled together so as to form a circular pipe, thereby beingconnected to an exhaust-gas upstream side end portion 6 c of the pipecollecting part 6.

An exhaust-gas downstream side end portion 6 f of the pipe collectingpart 6 is connected with an exhaust-gas side upstream side end portionof the catalytic converter 7 which contains a catalyst carrier 8.

An exhaust-gas downstream side end portion of the catalytic converter 7is provided with a flange portion 9 for fixing a not-shown downstreamside exhaust pipe.

As shown in FIGS. 3 to 7, the pipe collecting part 6 is made of a pairof divided bodies 6 a and 6 b, formed by using a not-shown press formingmachine, which are coupled and welded with each other at their edgeportions X1 and X2 to form like a tube. The exhaust-gas upstream sideend portion 6 c of the pipe collecting part 6 has an opening forreceiving the exhaust-gas downstream portions of the branch pipes 2 to5. An intermediate portion of the pipe collecting part 6 is formed as areduced diameter portion 6 d. In the reduced diameter part 6, lengths ofsurfaces orthogonal to surfaces on which the branch pipes 2 to 5 arebent like the L-letter shape is shorten compared to lengths of thelatter surfaces. In other words, the reduced diameter portion 6 d isformed so that the length of the pipe collecting part 6 in thelongitudinal direction, indicated by an arrow LN in FIG. 1, of the headflange 1 is set to be shorter than the length of the pipe collectingpart 6 in a thickness direction, indicated by an arrow LT in FIG. 2,where the longitudinal direction LN also corresponds to a longitudinaldirection of the engine and the thickness direction LT also correspondsto a lateral direction of the engine.

As shown in FIG. 5, an opening portion 6 e is formed, for receiving theoxygen sensor 10, on one of the surfaces of the reduced diameter portion6 d, namely on the surface seen from the longitudinal direction LN ofthe head flange 1 as shown in FIG. 1 and FIG. 2. The oxygen sensor 10 isfixed along the longitudinal direction LN, and it serves as a sensor ofthe present invention.

An opening of the exhaust-gas downstream side end portion 6 f of thepipe collecting part 6 is expanded in diameter so as to receive anexhaust-gas upstream side end portion of the catalytic converter 7.

The pipe collecting part 6 is formed to have an outer shape describedbelow. As shown in FIG. 3 and FIG. 4, the outer shape is formed in sucha way that the outer profiles, seen from in the thickness direction LT,of the surfaces, seen from the longitudinal direction LN, are formedlike an involute curve, from the exhaust-gas upstream side end portion 6c to the exhaust-gas downstream side end portion 6 f, thereby providingthe intermediate portion thereof to be reduced in diameter. Accordingly,as shown in FIG. 5 and FIG. 6, the outer profiles of the surfaces, seenfrom the thickness direction LT, are formed like a gradually expandingcurve from the exhaust-gas upstream side end portion to the exhaust-gasdownstream side end portion.

As shown in FIG. 1 and FIG. 2, the oxygen sensor 10 is used fordetecting an oxygen concentration in the exhaust gas passing through thepipe collecting part 6 to carry out feedback control of an air-fuelratio of an air-fuel mixture to be supplied to the engine. One endportion of the sensor 10 is provided with a wiring 10 a electricallyconnected to a not-shown control unit, the intermediate portion thereofis formed with a holding portion 10 b contacted with a cylindrical bossmember 11 provided on the opening portion 6 e of the pipe collectingpart 6, and the other end portion thereof is provided with a sensingpart 10 c arranged at a center position of a flow of the exhaust gaswhen it is inserted into the opening portion 6 e of the pipe collectingpart 6.

At least the head flange 1, the branch pipes 2 to 5, the pipe collectingpart 6 and the catalytic converter 7 are made of metal like stainless.Thus constructed exhaust manifold EM is connected with the cylinder headof the engine through the head flange 1, and the flange portion 9 of thecatalytic converter 8 is connected with the downstream side exhaust pipeattached to the vehicle body when they are mounted on the vehicle body.

Next the operation of the exhaust manifold EM of the embodiment will bedescribed.

Before that, the problem of the conventional exhaust manifold will beexplained below.

In the conventional exhaust manifold, each branch pipe 02 of the exhaustmanifold EM is formed to bend from the head flange 01 like the L-lettershape, the exhaust-gas upstream side end portion thereof being fixed tothe engine through the head flange 01, and the exhaust-gas downstreamside end portion thereof being fixed to the vehicle body through thecatalytic converter 07 and others. Therefore, a stress is produced dueto the thermal expansion and contraction of each branch pipe and alsodue to the vibrations of the engine, thereby acting on the whole exhaustmanifold to be folded like the L-letter shape. In order to avoid thisfolding, the pipe collecting part 06 requires to be enforced in strengththereof by increasing the thickness of the pipe collecting part 06. Thisincrease in the thickness causes the problems in that the temperaturerise in the exhaust gas purifying catalyst is delayed due to theincrease in its mass and thermal capacity.

On the other hand, in the exhaust manifold EM of the embodiment, thereduced diameter part 6 c of the pipe collecting part 6 is not formed insuch a way that the lengths of the surfaces, parallel to the surfaceextending along which the branch pipes 2 to 5 are bent, are reduced indiameter. This can ensure the pipe collecting part 6 to have thestrength enough to bear the stress due to the thermal expansion andcontraction of the branch pipes 2 to 5 and due to the vibration of theengine, without increasing the thickness of the pipe collecting part 6.

In addition, in the exhaust manifold of the embodiment, the reduceddiameter portion 6 d is formed so that the lengths of the surfaces,orthogonal to the surfaces along which the branch pipes 2 to 5 are bent,are set to be shorter than the length of the latter surface, and theoxygen sensor 10 is provided on the reduced diameter portion 6 d. Thisenables the oxygen sensor 10 to detect the state of the exhaust gas withhigh accuracy, because the sensing part 10 c of the oxygen sensor 10 canbe positioned in the center of a flow of the exhaust gas passing thereduced cross section of the pipe collecting part 6.

Next the advantages of the exhaust manifold EM of the embodiment will bedescribed.

As described above, in the exhaust manifold EM of the embodiment, theplurality of branch pipes 2 to 5 is formed to bend from the head flange1 like the L-letter shape, the exhaust-gas upstream side end portions ofthe branch pipes 2 to 5 are connected with the engine through the headflange 1, and the exhaust-gas downstream side end portions thereof areconnected with the pipe collecting part 6, which is provided with theoxygen sensor 10 for detecting the state of the exhaust gas. The reduceddiameter portion 6 d of the pipe collecting part 6 is formed so thatlengths of the surfaces, orthogonal to the surfaces along which thebranch pipes 2 to 5 are bent like the L-letter shape, are set to beshorter than those of the latter surfaces. The reduced diameter portion6 d is provided with the oxygen sensor 10. Therefore, the exhaustmanifold EM of the embodiment can increase its strength withoutincreasing the weight of the pipe collecting part 6. This can improveits exhaust gas purifying performance by accelerating the temperaturerise in the catalyst carrier (an exhaust gas purifying catalyst) 8 inthe catalytic converter 7. In addition, the oxygen sensor 10 can detectthe state of the exhaust gas with high accuracy because it is located inthe center of the flow of the exhaust gas passing through the reduceddiameter portion 6 d.

The both surfaces, seen from the longitudinal direction LN, of thereduced diameter portion 6 are formed like the involute curve. Theinvolute curved surfaces facilitate dispersion of the stress acting onthe surfaces, thereby increasing the strength of the reduced diameterportion 6 d.

The both surfaces, seen from the thickness direction LT, of the pipecollecting part 6 is formed to have the curve at their side edgeportions so that longitudinal directional (width) lengths of thesurfaces are set to be larger from the exhaust-gas upstream side endportion to the exhaust-gas downstream side end portion. This profile canensure the pipe collecting part 6 to bear the stress acting on thesurfaces.

The pipe collecting part 6 consists of the two divided bodies 6 a and 6b, which are firstly separated in the longitudinal direction LN alongthe thickness direction LT and then are coupled with each other.Therefore, the pipe collecting part 6 can be manufactured easily and atlow costs.

The oxygen sensor 10 is provided so that the holding portion 10 b isplaced on one of the surfaces seen from the longitudinal direction LN,via the cylindrical boss member 11. Therefore, the cylindrical bossportion 11 and the holding portion 10 b can increase the strength of thesurface provided therewith. In addition, they can reduce a projectingamount of the oxygen sensor 10 from the pipe collecting part 6, and canavoid the oxygen sensor 6 from possible interferences with otherportions/parts.

It is understood that the invention is not limited to theabove-described embodiment but that various changes and/or modificationsmay be made without departing from the spirit and/or the scope of thepresent invention. For example, the oxygen sensor 10 is provided on theone surface, seen from the longitudinal direction LN, of the reduceddiameter portion 6 d of the pipe collecting part 6 in the embodiment,while it may be provided on the other surface of the reduced diameterportion 6 d.

The sensor of the present invention is not limited to the oxygen sensor,and it may employ a sensor for detecting a state of the exhaust gas, forexample, a temperature sensor for detecting a temperature of the exhaustgas.

In the embodiment, the pipe collecting part 6 is manufactured by the twodivided bodies 6 a and 6 b being coupled with each other, while it maybe made of one pipe by using press working, spinning or the like.

INDUSTRIAL AVAILABILITY

The exhaust manifold EM of the present invention is applicable toexhaust manifolds of various engines, including transversely mountedengines and longitudinally mounted engines, as long as the engines usean exhaust manifold for discharging exhaust gas therethrough.

1. An exhaust manifold comprising: a head flange fixed to an engine; aplurality of branch pipes which is bent downward from the head flange toform like an L-letter shape, the branch pipes having exhaust-gasupstream side end portions and exhaust-gas downstream side end portionswhere the exhaust-gas upstream side end portions are connected with theengine through the head flange; and a pipe collecting part connectedwith the exhaust-gas downstream side end portions of the branch pipes,the pipe collecting part being provided with a sensor for detecting astate of an exhaust gas, wherein the pipe collecting part has a reduceddiameter portion in which a length, of the pipe collecting part, in alongitudinal direction of the head flange is set to be shorter than alength, of the pipe collecting part, in a thickness direction of thehead flange, the reduced diameter portion being provided with thesensor.
 2. The exhaust manifold according to claim 1, wherein the pipecollecting part has an intermediate portion in which the both surfacesseen from the thickness direction are formed to have an involute curve.3. The exhaust manifold according to claim 3, wherein the pipecollecting part is formed to have curves at both sides, respectively, sothat width lengths of the surfaces seen from the thickness directionbecome larger from an exhaust-gas upstream side end portion of the pipecollecting part to an exhaust-gas downstream side end portion thereof.4. The exhaust manifold according to claim 3, wherein the pipecollecting part has two divided bodies, which are separatable in thelongitudinal direction along the thickness direction, coupled with eachother.
 5. The exhaust manifold according to claim 5, wherein the sensorhas a holding portion which is fixed on one of the surfaces seen fromthe longitudinal direction through a boss member provided thereon. 6.The exhaust manifold according to claim 2, wherein the pipe collectingpart has two divided bodies, which are separatable in the longitudinaldirection along the thickness direction, coupled with each other.
 7. Theexhaust manifold according to claim 6, wherein the sensor has a holdingportion which is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.
 8. The exhaustmanifold according to claim 2, wherein the sensor has a holding portionwhich is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.
 9. The exhaustmanifold according to claim 1, wherein the pipe collecting part isformed to have curves at both sides, respectively, so that width lengthsof the surfaces seen from the thickness direction become larger from anexhaust-gas upstream side end portion of the pipe collecting part to anexhaust-gas downstream side end portion thereof.
 10. The exhaustmanifold according to claim 9, wherein the pipe collecting part has twodivided bodies, which are separatable in the longitudinal directionalong the thickness direction, coupled with each other.
 11. The exhaustmanifold according to claim 10, wherein the sensor has a holding portionwhich is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.
 12. The exhaustmanifold according to claim 9, wherein the sensor has a holding portionwhich is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.
 13. The exhaustmanifold according to claim 1, wherein the pipe collecting part has twodivided bodies, which are separatable in the longitudinal directionalong the thickness direction, coupled with each other.
 14. The exhaustmanifold according to claim 13, wherein the sensor has a holding portionwhich is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.
 14. The exhaustmanifold according to claim 1, wherein the sensor has a holding portionwhich is fixed on one of the surfaces seen from the longitudinaldirection through a boss member provided thereon.